26 Algorithms library [algorithms]

26.7 Mutating sequence operations [alg.modifying.operations]

26.7.8 Remove [alg.remove]

template<class ForwardIterator, class T = iterator_traits<ForwardIterator>::value_type> constexpr ForwardIterator remove(ForwardIterator first, ForwardIterator last, const T& value); template<class ExecutionPolicy, class ForwardIterator, class T = iterator_traits<ForwardIterator>::value_type> ForwardIterator remove(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, const T& value); template<class ForwardIterator, class Predicate> constexpr ForwardIterator remove_if(ForwardIterator first, ForwardIterator last, Predicate pred); template<class ExecutionPolicy, class ForwardIterator, class Predicate> ForwardIterator remove_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Predicate pred); template<permutable I, sentinel_for<I> S, class Proj = identity, class T = projected_value_t<I, Proj>> requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*> constexpr subrange<I> ranges::remove(I first, S last, const T& value, Proj proj = {}); template<forward_range R, class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>> requires permutable<iterator_t<R>> && indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> constexpr borrowed_subrange_t<R> ranges::remove(R&& r, const T& value, Proj proj = {}); template<execution-policy Ep, random_access_iterator I, sized_sentinel_for<I> S, class Proj = identity, class T = projected_value_t<I, Proj>> requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*> subrange<I> ranges::remove(Ep&& exec, I first, S last, const T& value, Proj proj = {}); template<execution-policy Ep, sized-random-access-range R, class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>> requires permutable<iterator_t<R>> && indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> borrowed_subrange_t<R> ranges::remove(Ep&& exec, R&& r, const T& value, Proj proj = {}); template<permutable I, sentinel_for<I> S, class Proj = identity, indirect_unary_predicate<projected<I, Proj>> Pred> constexpr subrange<I> ranges::remove_if(I first, S last, Pred pred, Proj proj = {}); template<forward_range R, class Proj = identity, indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred> requires permutable<iterator_t<R>> constexpr borrowed_subrange_t<R> ranges::remove_if(R&& r, Pred pred, Proj proj = {}); template<execution-policy Ep, random_access_iterator I, sized_sentinel_for<I> S, class Proj = identity, indirect_unary_predicate<projected<I, Proj>> Pred> subrange<I> ranges::remove_if(Ep&& exec, I first, S last, Pred pred, Proj proj = {}); template<execution-policy Ep, sized-random-access-range R, class Proj = identity, indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred> requires permutable<iterator_t<R>> borrowed_subrange_t<R> ranges::remove_if(Ep&& exec, R&& r, Pred pred, Proj proj = {});
Let E be
  • bool(*i == value) for remove;
  • bool(pred(*i)) for remove_if;
  • bool(invoke(proj, *i) == value) for ranges​::​remove;
  • bool(invoke(pred, invoke(proj, *i))) for ranges​::​remove_if.
Preconditions: For the algorithms in namespace std, the type of *first meets the Cpp17MoveAssignable requirements (Table 33).
Effects: Eliminates all the elements referred to by iterator i in the range [first, last) for which E holds.
Returns: Let j be the end of the resulting range.
Returns:
  • j for the overloads in namespace std.
  • {j, last} for the overloads in namespace ranges.
Complexity: Exactly last - first applications of the corresponding predicate and any projection.
Remarks: Stable ([algorithm.stable]).
[Note 1: 
Each element in the range [ret, last), where ret is the returned value, has a valid but unspecified state, because the algorithms can eliminate elements by moving from elements that were originally in that range.
— end note]
template<class InputIterator, class OutputIterator, class T = iterator_traits<InputIterator>::value_type> constexpr OutputIterator remove_copy(InputIterator first, InputIterator last, OutputIterator result, const T& value); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class T = iterator_traits<ForwardIterator1>::value_type> ForwardIterator2 remove_copy(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, const T& value); template<class InputIterator, class OutputIterator, class Predicate> constexpr OutputIterator remove_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class Predicate> ForwardIterator2 remove_copy_if(ExecutionPolicy&& exec, ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 result, Predicate pred); template<input_iterator I, sentinel_for<I> S, weakly_incrementable O, class Proj = identity, class T = projected_value_t<I, Proj>> requires indirectly_copyable<I, O> && indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*> constexpr ranges::remove_copy_result<I, O> ranges::remove_copy(I first, S last, O result, const T& value, Proj proj = {}); template<input_range R, weakly_incrementable O, class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>> requires indirectly_copyable<iterator_t<R>, O> && indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> constexpr ranges::remove_copy_result<borrowed_iterator_t<R>, O> ranges::remove_copy(R&& r, O result, const T& value, Proj proj = {}); template<execution-policy Ep, random_access_iterator I, sized_sentinel_for<I> S, random_access_iterator O, sized_sentinel_for<O> OutS, class Proj = identity, class T = projected_value_t<I, Proj>> requires indirectly_copyable<I, O> && indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*> ranges::remove_copy_result<I, O> ranges::remove_copy(Ep&& exec, I first, S last, O result, OutS result_last, const T& value, Proj proj = {}); template<execution-policy Ep, sized-random-access-range R, sized-random-access-range OutR, class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>> requires indirectly_copyable<iterator_t<R>, iterator_t<OutR>> && indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> ranges::remove_copy_result<borrowed_iterator_t<R>, borrowed_iterator_t<OutR>> ranges::remove_copy(Ep&& exec, R&& r, OutR&& result_r, const T& value, Proj proj = {}); template<input_iterator I, sentinel_for<I> S, weakly_incrementable O, class Proj = identity, indirect_unary_predicate<projected<I, Proj>> Pred> requires indirectly_copyable<I, O> constexpr ranges::remove_copy_if_result<I, O> ranges::remove_copy_if(I first, S last, O result, Pred pred, Proj proj = {}); template<input_range R, weakly_incrementable O, class Proj = identity, indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred> requires indirectly_copyable<iterator_t<R>, O> constexpr ranges::remove_copy_if_result<borrowed_iterator_t<R>, O> ranges::remove_copy_if(R&& r, O result, Pred pred, Proj proj = {}); template<execution-policy Ep, random_access_iterator I, sized_sentinel_for<I> S, random_access_iterator O, sized_sentinel_for<O> OutS, class Proj = identity, indirect_unary_predicate<projected<I, Proj>> Pred> requires indirectly_copyable<I, O> ranges::remove_copy_if_result<I, O> ranges::remove_copy_if(Ep&& exec, I first, S last, O result, OutS result_last, Pred pred, Proj proj = {}); template<execution-policy Ep, sized-random-access-range R, sized-random-access-range OutR, class Proj = identity, indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred> requires indirectly_copyable<iterator_t<R>, iterator_t<OutR>> ranges::remove_copy_if_result<borrowed_iterator_t<R>, borrowed_iterator_t<OutR>> ranges::remove_copy_if(Ep&& exec, R&& r, OutR&& result_r, Pred pred, Proj proj = {});
Let E(i) be
  • bool(*i == value) for remove_copy;
  • bool(pred(*i)) for remove_copy_if;
  • bool(invoke(proj, *i) == value) for ranges​::​remove_copy;
  • bool(invoke(pred, invoke(proj, *i))) for ranges​::​remove_copy_if.
Let:
  • M be the number of iterators i in [first, last) for which E(i) is false;
  • result_last be result + M for the overloads with no parameter result_last or result_r;
  • N be min(M,  result_last - result).
Mandates: *first is writable ([iterator.requirements.general]) to result.
Preconditions: The ranges [first, last) and [result, result + N) do not overlap.
[Note 2: 
For the parallel algorithm overloads in namespace std, there can be a performance cost if iterator_traits<ForwardIterator1>​::​value_type does not meet the Cpp17MoveConstructible (Table 31) requirements.
For the parallel algorithm overloads in namespace ranges, there can be a performance cost if iter_value_t<I> does not model move_constructible.
— end note]
Effects: Copies the first N elements referred to by the iterator i in the range [first, last) for which E(i) is false into the range [result, result + N).
Returns:
  • result + N, for the algorithms in namespace std.
  • {last, result + N}, for the algorithms in namespace ranges, if N is equal to M.
  • Otherwise, {j, result_last}, for the algorithms in namespace ranges, where j is the iterator in [first, last) for which E(j) is false and there are exactly N iterators i in [first, j) for which E(i) is false.
Complexity: At most last - first applications of the corresponding predicate and any projection.
Remarks: Stable ([algorithm.stable]).